Jute is an eco-friendly and biodegradable natural fiber. It is a renewable resource with high biomass production per unit area of land. More than 100 jute species (including wild relatives) produce natural bast fiber. Jute is produced from plants in the genus Corchorus, which was once classified with the family Tiliaceae, more recently with Malvaceae. However, only two of these species, C. olitorius and C. capsularis, produce high quality fiber suitable for use in industrial purposes. Being a natural fiber, jute can be used in various ways, supplementing or replacing synthetics, and it has been receiving increasing attention from industry. As there is an increasing global demand for jute fiber, further improvement of jute fiber production is necessary. Thus, there is a significant interest in studying fiber biosynthesis and exploring the molecular biology involved in biosynthesis of this fiber.
Fiber of jute is an extraxylary fiber which is composed of and/or comprises two types of fiber: (i) primary phloem fiber that develops from procambium in the protophloem region through cell division and modification, and (ii) secondary phloem fiber that develops from cambium by the activity of fusiform and ray initials (Maiti and Mitra, 1972. Bull Bot Soc Bengal 26:79-85). These procambium and cambium tissues communicate cell-to-cell mediated by the tracheary element differentiation inhibitory factor (TIDF) and the TDIF receptor (TDR) membrane protein kinase, which promotes proliferation of procambial cells and suppresses their xylem differentiation (FIG. 1; Hirakawa et al., 2010. Plant Cell, 22:2618-2629; Etchells et al., 2013. Development 140, 2224-2234).
The WUSCHEL-related HOMEOBOX (WOX) gene family performs related functions during initiation and/or maintenance of various embryonic, meristematic, and organ initial cells (Haecker et al., 2004). Among the WUSCHEL-related HOMEOBOX (WOX) gene family proteins, WOX4 acts as a key regulator of TDIF signaling pathway (Hirakawa et al. 2010) and expressed preferentially in the procambium and cambium (Schrader et al., 2004; Ji et al., 2010 and Hirakawa et al. 2010). For example, TDIF-TDR induces the transcription of master transcription factor WUSCHEL-related HOMEOBOX4 (WOX4) that promotes the maintenance of procambium/cambium stem cells in Arabidopsis and in Tomato. WUSCHEL-related HOMEOBOX4 (WOX4) polypeptide catalyzes the initiation of bast fiber in plant. However, there are not many characterization reports or existing technologies provided in the prior art relating to this polypeptide. U.S. Patent No. 2011/0283420 A1 (incorporated by reference) has disclosed wuschel related homeobox 1-like (WOX1-like) polypeptide for enhanced yield-related traits in plants. In another E.P. Patent No. 1451301 B1 disclosed the use of wuschel gene in promotion of somatic embryogenesis in plants. Recently, some wuschel gene homologs were disclosed in U.S. Patent No. 2010/0100981 A1 (incorporated by reference).
In view of the fact that WUSCHEL-related homeobox4 protein could play an important role in the biosynthesis pathway of jute fiber, it is desirable for industry to provide a genetic approach relating to the biosynthesis of the fiber in the plant by exploring and utilizing the molecular biology and genetic information of WUSCHEL-related homeobox4 (WOX4). Besides, because the fiber biosynthesis pathway and genetic make-up of each species of plant typically varies, a species-specific approach is also preferable in order to optimize yield of fiber from jute plants, and obtain compatible results to enable use in industry.